Typically in a case where a vacuum pump such as a turbo-molecular pump is attached to a vacuum chamber of a vacuum processing device, a vacuum valve is interposed. Patent Literature 1 (U.S. Pat. No. 5,577,707) discloses such a vacuum valve.
The vacuum valve described in Patent Literature 1 includes a valve housing configured such that a pair of openings is formed at opposing surfaces and a gas flow path is provided at a center portion, and a valve body detachably inserted into the opening by swinging between the openings. The vacuum valve further includes, in the valve housing, an annular sealing body surrounding the openings. The sealing body contacts a peripheral edge of the valve body driven to a fully-closed position, thereby pressing the valve body against the valve housing. In this manner, the gas flow path is blocked by the valve body.
The sealing body described in Patent Literature 1 uses a compression spring as the drive force of pressing the valve body toward the valve housing, and uses compressed air (air pressure) as drive force against the drive force of the compression spring. For example, for a reason of the air pressure being supplied by a compressor driven by power of an external power source, the drive force against the compression spring sometimes cannot be obtained by the air pressure upon blackout.
In the vacuum valve described in Patent Literature 1, when blackout occurs in a state in which the sealing body is controlled to a proper position by the drive force of the compressed air, if the valve body is not at the fully-closed position, the sealing body might be driven to a undesired position, leading to a tilting posture of the sealing body with respect to the openings, for example.